Abstract: A time-domain reflection method based on the transmission line equivalent distribution parameter model is proposed to cope with the difficulty in detecting and locating the fault of DC cables in large-scale photovoltaic power stations,and the anti-interference performance of this method is also improved by expanding the frequency spectrum. In this paper,the causes and types of cable faults in photovoltaic power plants are studied. The spread spectrum and time domain reflection are theoretically analyzed as well. Then the theoretical correctness is verified by simulation and experiment after analyzing the feasibility and anti-interference ability of this method in combination with different working conditions. The experimental results showed that the proposed method provides a stable way to achieve online detection and accurate location of DC cable faults in photovoltaic systems.